1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device such as a light emitting diode (LED).
2. Description of the Related Art
Recently, a semiconductor devices such as an LED has been required to be thinner in order to miniaturize a package for sealing the semiconductor device or directly mount the semiconductor device on a printed circuit board or the like.
As such a semiconductor device, an epi film LED has been suggested. This epi film LED can be realized by epitaxially growing semiconductor layers including an n-type semiconductor layer, an active semiconductor layer and a p-type semiconductor layer on a growth substrate, separating the grown semiconductor layers from the growth substrate, and forming electrodes on both surfaces of the grown semiconductor layers. Since the epi film LED is formed by only the semiconductor layers without the growth substrate, the epi film LED is very thin, i.e., about 3 to 10 μm thick.
In a first prior art method for manufacturing an epi film LED (see: JP-P2003-51611 A), an underlayer made of AlGaN, for example, and semiconductor layers including an n-type semiconductor layer, an active semiconductor layer and a p-type semiconductor layer are sequentially epitaxially-grown on a front surface of a growth substrate made of transparent sapphire by a metal organic chemical vapor deposition (MOCVD) process. Next, a dry etching process such as a reactive ion etching (RIE) process is carried out to form element isolation grooves for partitioning the semiconductor layers for every semiconductor element (chip), the element isolation grooves reaching the underlayer. Next, a back surface of the growth substrate is exposed with laser light whose energy is between an energy gap of the underlayer and an energy gap of one of the semiconductor layers adjacent to the underlayer to create ablations therebetween, so that the epitaxially-grown semiconductor layers are easily separated from the growth substrate along with the underlayer. Finally, electrodes are formed on both surfaces of the separated semiconductor layers to complete the semiconductor elements (chips).
In a second prior art method for manufacturing a semiconductor device (see: JP-P2004-172351 A), instead of the underlayer of the first prior art method, an exfoliation layer made of AlAs, for example, is provided between the growth substrate and the epitaxially-grown semiconductor layers. In this case, the growth substrate may be opaque, and is made of GaAs, for example. Then, the exfoliation layer is removed by a wet etching process using buffered fluoric acid or hydrogen fluoride (HF), so that the epitaxially-grown semiconductor layers are easily separated from the growth substrate.
In the above-described first and second prior art methods, however, when the separated epitaxially-grown semiconductor layers are subject to an evaporating process, a photolithography process and an etching process for forming the electrodes thereon, the separated semiconductor layers would be easily broken, thus decreasing the manufacturing yield.